In the filed of clamps, bar clamps are a well known tool having many and varied applications. The concept of a bar clamp is old and well-known. In recent years, bar clamps have been developed which can be operated by one hand, and are held by a friction member. A trigger handle advances a slide bar by driving a lever which binds against a surface of the slide bar and moves the bar as the lever is moved. The lever is returned by spring force to its original position after each stroke of the trigger handle, the lever sliding over the bar surface during its return motion, (i.e. U.S. Pat. No. 4,926,722 by Sorensen et al. and U.S. Pat. No. 5,022,137 by Sorensen et al.). While very successful, these devices have a distinct limitation in clamping force. Specifically, the force exerted between clamping jaws is determined by the pressure applied to the lever by a user's grip. Thus, while a person with a strong grip can apply more pressure than a person with a weak grip, the pressure applied is still limited to human strength. Additionally, the force applied is difficult to control, relying on an individual user's judgment of how much pressure is being applied.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
An object of the present invention is to provide a bar clamp wherein the clamping pressure can be adjusted.
Another object of the present invention is to provide a bar clamp that can provide great clamping pressure through mechanical advantage.